We intend to study the protein-nucleic acid interactions which determine the specificity of initiation of the transcription and translation of messenger RNAs in bacteria. Previous work has provided 1) some knowledge of the oligonucleotide sequences which are recognized when RNA polymerases begin synthesis or when ribosomes initiate a polypeptide chain; and 2) the realization that alteration of these recognition phenomena is important to both normal cellular development and the successs of viral infection. However we still lack a detailed understanding of how ribosomes and polymerases recognize start signals and how control over gene expression is exerted at these points. The molecular mechanism of transcriptional and translational initiation will be examined using several systems. 1) Further studies on the interaction of mRNA and rRNA during the initiation of protein biosynthesis will be conducted. 2) Late bacteriophage T7 promoters will be examined to identify common features in recognition sites for T7 RNA polymerase. 3) Promoters and ribosomal RNA transcripts will be analyzed to establish the sequence of the promoters, number of RNA start sites, the nature of RNase III cleavage sites, etc. 4) Insertion sequences are also being examined to determine nucleic acid structures and protein factors required for transposition of these elements.